Forecasters say an omega block, a weather phenomenon named for its resemblance to the Greek letter, has hovered over much of the U.S. and parts of Canada since the second week of November, locking areas into unseasonable conditions.

Under an omega block, air over the southwest U.S. is pushed north into Canada before dropping back south into the southeast U.S. by a massive high-pressure ridge in the centre. The region to the left of the block gets above-average temperatures, while the region to the right gets below-average temperatures.

The system that's brought record-shattering warm weather to Alaska hasn't been so kind to the London area, where sub-zero temperatures and flurries have become the November norm.

But there's relief in sight.

"Right now the omega block will likely break down by the end of this week," said Environment Canada meteorologist Geoff Coulson. "We'll get back to more seasonal temperatures for the coming weekend."

Though omega blocks lock areas into weather patterns with little relief, a strong low-pressure system from Texas brought the recent rain and heavy winds to Southwestern Ontario, Coulson said.